Mycoplasma hyopneumoniae is the etiologic agent of swine mycoplasmal pneumonia. This disease is an important cause of economic loss in the swine industry due to reduced weight gain and poor feed efficiency. The disease causes a chronic cough, dull hair coat, retarded growth and unthrifty appearance lasting several weeks. Characteristic lesions of purple to gray areas of consolidation, particularly in ventral apical and cardiac lobes are observed in infected animals. Although the disease causes little mortality, affected swine are often prone to secondary infections by opportunistic pathogens, resulting in death or stress. Economic losses alone have been estimated at between 200 to 250 million dollars annually.
Mycoplasma hyopneumoniae is a slow growing, fastidious bacterium which lacks a cell wall. It is frequently difficult to isolate from the respiratory tract due to Mycoplasma hyorhinis, a common secondary agent also located in the respiratory tract. The disease is spread by aerosol, produced by coughing, and by direct contact from an affected or convalescent carrier swine. Mingling of infected animals and uninfected animals results in early and frequent reinfection. Infection frequently starts with infection of piglets by carrier sows at farrowing. Due to herd management techniques, infection may not become evident until later in life. Additional infection usually is observed after weaning when pigs are pooled. Overt disease is normally observed in pigs at six weeks of age or older. Grown rates and feed conversion rates are markedly reduced in affected animals. Treatments using antibiotics are expensive and require prolonged use. Reinfection is also a problem. Vaccines are presently the most effective method for avoiding infections and their consequences.
Fort Dodge Animal Health (FDAH) markets Mycoplasma hyopneumoniae bacterin under the name Suvaxyn® Respifend® MH for use as a vaccine to protect healthy swine against clinical signs caused by Mycoplasma hyopneumoniae. The vaccine contains Carbopol as an adjuvant and is recommended as a two-dose vaccine for pigs at least one-week old, with the second dose two to three weeks after the first vaccination. However, a two-dose vaccine has the obvious disadvantage of requiring a second handling of the animals in order to provide full protection against disease.
It is therefore an object of this invention to provide an effective vaccine against Mycoplasma hyopneumoniae that elicits protective immunity and prevents disease caused by this organism with an administration of a single dose of vaccine.
It is another object of this invention to provide a vaccine composition suitable for use in swine against infection and disease caused by Mycoplasma hyopneumoniae, and which may be used in combination with other bacterins and/or toxoids.
It is a still further object of the present invention to provide a method for the prevention or amelioration of the disease wherein the causative organism is Mycoplasma hyopneumoniae by utilizing an adjuvant formulation which enhances the immunogenicity of the bacterin so as to elicit protective immunity after a single dose of the vaccine.
Other objects and features of this invention will become apparent from the detailed description set forth hereinbelow.